1. Field of the Invention
The present invention relates to the structure of a body of a motor vehicle and, in particular, to a side sill structure for the body of the motor vehicle.
2. Description of Related Art
As this kind of conventional structure, there is known one in Japanese Published Unexamined Patent Application No. 18784/1989. In this prior art, inside each side sill in which a front pillar, a center pillar and a rear pillar are respectively disposed in a manner extending upwards, there is contained a pipelike reinforcing member by supporting it near three crossing points between each of the pillars and the side sill.
In Japanese Published Unexamined Utility Model Registration Application No. 87668/1983, there is known the following structure. Namely, a pipelike member is contained inside each side sill by supporting the pipelike member on its both ends, and there is further filled a foamed material between the pipelike member and an internal wall of the side sill, thereby preventing the crippling of the side sill. In the description of this specification, such a member as will be provided on both widthwise sides of the body of the motor vehicle (e.g., a side sill, a center pillar) is sometimes expressed in terms of a singular form for the sake of simplicity. It should, however, be understood that such an expression is intended to denote "each" of such members where necessary.
Among the forces to act on the body of the motor vehicle, when an external force to push the center pillar, e.g., inwards of the body of the motor vehicle is acted on or operated, the external force is transmitted to a floor panel via the side sill. On the other hand, the floor panel is provided, for the purpose of reinforcement, with a cross member which extends in the widthwise direction of the body of the motor vehicle, by connecting it to the side sill. It follows that, when the external force is acted on the center pillar, the center pillar is supported by the cross member via the side sill. By the way, the cross member must on some occasions be offset from the center pillar due to the position of mounting a seat, or the like. If the cross member is offset from the center pillar, the external force to act on the center pillar acts, as a torsional moment, on that portion of the side sill which lies between the center pillar and the cross member. This will bring about a disadvantage in that the side sill in the shape of a box is deformed, resulting in a failure to sufficiently support the center pillar.
By the way, even if the pipelike reinforcing member is contained inside the side sill as in the above-described conventional structure, when the reinforcing member is supported on the side sill only at the three points, the side sill is not restrained by the reinforcing member in portions between respective supported points. Therefore, the twisting rigidity of the side sill is not increased much and, consequently, the external force acted on the center pillar cannot effectively be transmitted to the cross member. Though the crippling may be prevented by filling the clearance between the pipelike member and the internal wall of the side sill with the foamed material, the improvement in the twisting rigidity cannot be expected because the rigidity of the foamed material is low.